In construction machineries, ships, land devices, and the like, an oil-pressure motor or an electric motor is often used for rotary drive. In recent years, attempts to reduce energy consumption by using both the oil-pressure motor and the electric motor have been made. As one example, an electricity-oil hybrid motor has been developed, in which the oil-pressure motor and the electric motor are integrated by connecting a shaft of the oil-pressure motor and a shaft of the electric motor via a coupling. According to this electricity-oil hybrid motor, the oil-pressure motor and the electric motor are provided in the same casing, and the casing is filled with oil (see PTL 1, for example).